Mine-impacted Water Research Articles

Lead (Pb) removal from gold mining-impacted water utilizing palm oil fuel ash (POFA)

Mining, particularly gold mining, is a lucrative industry. However, it poses significant environmental risks, such as releasing heavy metal elements into the soil and water. After gold mines are exhausted, whether they are small or large scale, the excavated sites often need to be repaired. This situation has led to a global concern regarding the presence of heavy metals from mining activities, which are known to be carcinogenic and harmful to living organisms. The concentration of heavy metals in these areas often surpasses safety limits, necessitating advanced treatment methods for their removal, especially lead (Pb) compounds from gold mining waste. One effective treatment method is the adsorption process. This study examined POFA's inherent capacity to remove lead from water contaminated by gold mining without modification. This method was preferred due to its high efficiency and cost-effective option for removing heavy metal compounds. According to the experiment's results, the largest adsorption capacity of 0.816 mg/g was followed by the greatest removal efficiency of 91.837%. The isotherm analysis found that the Langmuir model provided an outstanding fit for the experimental data. Thus, this relationship suggested that on the surface of the POFA, a monolayer and an adsorption process suitable for physical adsorption took place.

Metal(loid)s Removal Response to the Seasonal Freeze–Thaw Cycle in Semi-passive Pilot Scale Bioreactors

There is an increasing demand for cost-effective semi-passive water treatment that can withstand challenging climatic conditions and effectively and sustainably manage mine-impacted water in (sub)arctic regions. This study investigated the ability of four pilot-scale bioreactors inoculated with locally sourced bacteria and affected by a freeze–thaw cycle to remove selenium and antimony. The bioreactors were operated at a Canadian (sub)arctic mine for a year. Two duplicate bioreactors were installed in a heated shed that was maintained at 5 °C over the winter, while two other duplicates were installed outdoors and left to freeze. The removal rate of selenium and antimony was monitored weekly, while a genomic characterization of the microbial populations in the bioreactors was performed monthly. The overall percentage of selenium and antimony removal was similar in the outside (10–93% Se, 20–96% Sb) and inside (35–94% Se, 10–95% Sb) bioreactors, apart from the spring thawing period when removal in the outdoor bioreactors was slightly lower for Se. The dominant taxonomic groups of microbial populations in all bioreactors were Bacteroidota, Firmicutes, Desulfobacterota and Proteobacteria. The microbial population composition was consistent and re-established quickly after spring thaw in the outside bioreactors. This demonstrated that the removal capacity of bioreactors inoculated with locally sourced bacteria was mostly unaffected by a freeze–thaw cycle, highlighting the strength of using local resources to design bioreactors in extreme climatic conditions.

Cryopurification and a Microbial Fuel Cell Process as a Combined Approach to Treat Mine-Impacted Water (Faro Mine, Yukon, Canada)

Cryopurification and a Microbial Fuel Cell Process as a Combined Approach to Treat Mine-Impacted Water (Faro Mine, Yukon, Canada)

Assessing viability of Escherichia coli in mining-impacted surface waters

Multiple threats to surface water quality, including both fecal pollution and acid mine drainage (AMD) are frequently coincident in mining regions, such as parts of the Appalachian region of the U.S. While it has been established that AMD can have toxic effects to fecal bacteria in surface waters, there is also evidence that AMD may induce a viable but non-culturable (VBNC) state, leaving fecal bacteria undetectable by common standard methods. This study aims to better understand the occurrence of VBNC Escherichia coli in mining-impacted waters (MIW) through three objectives: (1) assess the relationship between MIWs and concentrations of culturable fecal bacteria, (2) compare standard methods for quantification of E. coli in MIW, and (3) investigate whether MIW can induce a VBNC state in E. coli. An analysis of historic data from the Deckers Creek and West Run Watersheds of West Virginia revealed a moderate correlation between pH and E. coli abundance determined via culture and enzyme-based methods. In samples collected from sites within the two watersheds impacted by historic mining activities, the E. coli uidA gene was measured via quantitative polymerase chain reaction (qPCR) and found to be significantly more abundant than E. coli concentrations measured via culture or enzyme substrate coliform test. However, this discrepancy between methods was greatest in samples with a low pH. Further, experiments in which an environmental strain of E. coli was dosed into samples of MIW diluted with saline at different concentrations confirmed that the culturability of E. coli significantly decreased with increasing MIW concentration, while the total number of intact cells, determined via "live/dead” staining and microscopy, remained high. This finding suggests that culture and enzyme methods may underestimate viable E. coli levels in AMD-impacted waters.

PH and thiosulfate dependent microbial sulfur oxidation strategies across diverse environments.

Sulfur oxidizing bacteria (SOB) play a key role in sulfur cycling in mine tailings impoundment (TI) waters, where sulfur concentrations are typically high. However, our understanding of SOB sulfur cycling via potential S oxidation pathways (sox, rdsr, and S4I) in these globally ubiquitous contexts, remains limited. Here, we identified TI water column SOB community composition, metagenomics derived metabolic repertoires, physicochemistry, and aqueous sulfur concentration and speciation in four Canadian base metal mine, circumneutral-alkaline TIs over four years (2016 - 2019). Identification and examination of genomes from nine SOB genera occurring in these TI waters revealed two pH partitioned, metabolically distinct groups, which differentially influenced acid generation and sulfur speciation. Complete sox (csox) dominant SOB (e.g., Halothiobacillus spp., Thiomonas spp.) drove acidity generation and S2O3 2- consumption via the csox pathway at lower pH (pH ~5 to ~6.5). At circumneutral pH conditions (pH ~6.5 to ~8.5), the presence of non-csox dominant SOB (hosting the incomplete sox, rdsr, and/or other S oxidation reactions; e.g. Thiobacillus spp., Sulfuriferula spp.) were associated with higher [S2O3 2-] and limited acidity generation. The S4I pathway part 1 (tsdA; S2O3 2- to S4O6 2-), was not constrained by pH, while S4I pathway part 2 (S4O6 2- disproportionation via tetH) was limited to Thiobacillus spp. and thus circumneutral pH values. Comparative analysis of low, natural (e.g., hydrothermal vents and sulfur hot springs) and high (e.g., Zn, Cu, Pb/Zn, and Ni tailings) sulfur systems literature data with these TI results, reveals a distinct TI SOB mining microbiome, characterized by elevated abundances of csox dominant SOB, likely sustained by continuous replenishment of sulfur species through tailings or mining impacted water additions. Our results indicate that under the primarily oxic conditions in these systems, S2O3 2- availability plays a key role in determining the dominant sulfur oxidation pathways and associated geochemical and physicochemical outcomes, highlighting the potential for biological management of mining impacted waters via pH and [S2O3 2-] manipulation.

Naphthenic acid fraction compounds, produced by the extraction of bitumen from oil sands, alter survival and behaviour of juvenile yellow perch (Perca flavescens)

We evaluated whether naphthenic acid fraction compounds (NAFCs) extracted from oil sand tailings adversely affect fish survival and behaviour. Following a before–after-control-impact design, we housed wild-caught juvenile yellow perch ( Perca flavescens) in outdoor mesocosms to assess survival and behaviour under baseline conditions, then exposed fish to one of three treatments: negative control, 2 mg/L NAFC, or 15 mg/L NAFC. We performed behavioural assays (no-stimulus activity, food stimulus, and predator stimulus using a model bird) and assessed a comprehensive suite of endpoints (equilibrium losses, activity, shoaling, burst swimming, freezing, and space use). We found that exposure to 15 mg/L NAFCs substantially reduced fish survival and impaired fish equilibrium in all three behavioural tests. Furthermore, exposure to NAFCs impaired anti-predator behaviour: while the activity of control fish increased by two-fold in response to a predator stimulus, fish exposed to 2 or 15 mg/L NAFC did not change their activity levels after stimulation. No significant changes were observed in other behavioural endpoints. Overall, our findings suggest that a week-long exposure to NAFCs at concentrations commonly found in tailings ponds, constructed wetlands, and other mining-impacted waters may affect multiple facets of fish behaviour that could ultimately lead to reduced fitness in fish populations.

Mechanistic characterization of waterborne selenite uptake in the water flea, Daphnia magna, indicates water chemistry affects toxicity in coal mine-impacted waters.

Concentrations of selenium that exceed regulatory guidelines have been associated with coal mining activities and have been linked to detrimental effects on aquatic ecosystems and the organisms therein. Although the major route of selenium uptake in macroinvertebrates is via the diet, the uptake of waterborne selenite (HSeO3-), the prominent form at circumneutral pH, can be an important contributor to selenium body burden and thus selenium toxicity. In the current study, radiolabelled selenite (Se75) was used to characterize the mechanism of selenite uptake in the water flea, Daphnia magna. The concentration dependence (1-32μM) of selenite uptake was determined in 1-hour uptake assays in artificial waters that independently varied in bicarbonate, chloride, sulphate, phosphate and selenate concentrations. At concentrations representative of those found in highly contaminated waters, selenite uptake was phosphate-dependent and inhibited by foscarnet, a phosphate transport inhibitor. At higher concentrations, selenite uptake was dependent on waterborne bicarbonate concentration and inhibited by the bicarbonate transporter inhibitor DIDS (4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid). These findings suggest that concentrations of phosphate in coal mining-affected waters could alter selenite uptake in aquatic organisms and could ultimately affect the toxic impacts of selenium in such waters.

Microbiological Treatment of Nitrate and Selenate from Coal Mine-Affected Water in a Subsurface,Semi-Passive, and in situ Water Treatment Facility

Metallurgical coal mining generates significant amounts of waste rock, which can release nitrate and selenate upon atmospheric exposure, with resulting changes in surface water and ground water quality. Microorganisms residing on waste rock in the local subsurface have the metabolic potential to denitrifyand reduce selenium to treat mine-affected waters and stabilize waste rock. To support these processes, waste rock facilities have been designed to inject nutrients (e.g., methanol and phosphoric acid) in semi-passive water treatment of mine-impacted waters. Microbial community data regularly collected fromsubsurface semi-passive reactors throughout the startup and operations phases showed that native heterotrophic denitrifying bacteria and selenium reducing bacteria were enriched as a result of nutrient amendment. The microbial community was stable while the source water and geochemical parameters remained unchanged; however, a significant shift in the microbial community coincided with changes in the source of water treated. Metagenomic sequencing of microbial communities within the active treatment zone revealed multiple biochemical pathways of nitrate reduction. Geochemical and water quality data indicate near complete selenate reduction, yet a low abundance of in known selenate reduction genes were recovered. This may suggest that biologically mediated selenium reduction may be more widespread, both functionally and taxonomically. Further research into these pathways and mechanisms for nitrate and selenium reduction will help to strengthen our understanding of selenium reduction mechanisms and their application in mine water waste management.

The application of freezing technology for zinc removal from Faro pit mine-impacted water, Yukon, Canada

The application of freezing technology (cryopurification) could be a viable water treatment solution to the environmental industry, especially in northern climates as it holds several advantages, including high energy efficiency, the absence of chemical pre-treatment and cost-efficiency. The use of cryopurificiation in Northern Canada is of interest, considering three of the five largest federal contaminated mine sites where water treatment is typically required are located within Yukon and Northwest Territories. The current research aims to address the problem of elevated zinc concentrations in mine-impacted water (Faro Mine, Yukon, Canada) by applying cryopurification. The paper scope includes laboratory testing to quantitatively describe zinc removal from Faro Mine's water using cryopurification under various initial and boundary conditions. Based on laboratory testing results, zinc could be removed with an efficiency of above 75% and 95% using single-stage freezing under no mixing and constant mixing conditions, respectively and up to 97% in freezing-melting tests. The results reveal the purest ice production at freezing temperature range from −0.5 to −5 °C. Ice is purer with each subsequent melt fraction according to the results of freezing-melting laboratory tests. The addition of seed ice crystals enhances the purity of ice up to 10–14% and ice block shape has an effect on the purification process, as the results of laboratory testing show. The effect of mixing shows 23–72% improvement in overall removal efficiency depending on freezing temperature. The outcomes of current research form a foundation toward the development of an exceptional water treatment process utilizing northern climates' cold temperature conditions and having a potential to be scaled up.

Agarose-Immobilized LTA Zeolite: a Novel Material to Use in an Improved Treatment Process of Mine-Impacted Water

Agarose-Immobilized LTA Zeolite: a Novel Material to Use in an Improved Treatment Process of Mine-Impacted Water

Sulfidogenic Bioreactor-Mediated Formation of ZnS Nanoparticles with Antimicrobial and Photocatalytic Activity

The use of sulfidogenic bioreactors is a biotechnology trend to recover valuable metals such as copper and zinc as sulfide biominerals from mine-impacted waters. In the present work, ZnS nanoparticles were produced using "green" H2S gas generated by a sulfidogenic bioreactor. ZnS nanoparticles were physico-chemically characterized by UV-vis and fluorescence spectroscopy, TEM, XRD and XPS. The experimental results showed spherical-like shape nanoparticles with principal zinc-blende crystalline structure, a semiconductor character with an optical band gap around 3.73 eV, and fluorescence emission in the UV-visible range. In addition, the photocatalytic activity on the degradation of organic dyes in water, as well as bactericidal properties against several bacterial strains, were studied. ZnS nanoparticles were able to degrade methylene blue and rhodamine in water under UV radiation, and also showed high antibacterial activity against different bacterial strains including Escherichia coli and Staphylococcus aureus. The results open the way to obtain valorous ZnS nanoparticles from the use of dissimilatory reduction of sulfate using a sulfidogenic bioreactor.

Photocatalytic treatment of organoselenium in synthetic mine-impacted effluents.

Biological selenium reduction processes are commonly employed as the best available technology (BAT) for selenium removal; however, as a by-product they produce trace amounts of organoselenium compounds with orders of magnitude greater bioaccumulation potential and toxicity. Here, we assessed buoyant photocatalysts (BPCs) as a potential passive advanced oxidation process (P-AOP) for organoselenium treatment. Using a synthetic mine-impacted water solution, spiked with selenomethionine (96 μg/L) as a representative organoselenium compound, photocatalysis with BPCs fully eliminated selenomethionine to <0.01 μg/L with conversion to selenite and selenate. A theoretical reaction pathway was inferred, and a kinetics model developed to describe the treatment trends and intermediates. Given the known toxic responses of Lepomis macrochirus and Daphnia magna to organoselenium, it was estimated that photocatalysis could effectively eliminate organoselenium acute toxicity within a UV dose of 8 kJ/L (1-2 days solar equivalent exposure), by transformation of selenomethionine to less hazardous oxidized Se species. Solar photocatalysis may therefore be a promising passive treatment technology for selenium-impacted mine water management.

Biological and electrochemical treatments of coal mine-impacted water (MIW): toxicological evaluation on the duckweed Landoltia punctata

BackgroundTwo different coal mine-impacted water (MIW) treatments (biological via biostimulation of sulfate-reducing bacteria (SRB), and electrocoagulation (elC)) were proposed, reaching efficiencies of up to 99.79% in relation to SO42−, Fe, Mn, and Al ions, as well as acidity removals. The MIW, a high pollutant potential effluent, consists of river water impacted by coal acid mine drainage (AMD), which is acid, rich in sulfate and dissolved metallic ions, and consequently toxic. The aim of this study was to make a toxicological evaluation of MIW after biological and electrochemical treatments on Landoltia punctata, in order to verify the safeness and usability of the two treated waters. Material and methodsDuckweeds were exposed to different dilutions (0, 25, 50, 75, and 100% of samples) of the two treated waters, and the growth (r) and inhibition of growth (Ir) rates were calculated, based on 50% effect concentration (EC50). ResultsThe water from the biological treatment (microcosm assay) presented the highest toxicity (EC50 = 33.42%), even higher when compared to the raw MIW (EC50 = 42.78%), probably due to the hydrogen sulfide, that even after a purge removal, remained in solution. The results showed that this water, despite being within the standards in physicochemical terms, demonstrated risks in terms of toxicity. The water from electrocoagulation (elC) treatment, in the opposite way, showed much less toxicity, even lower than the control, and therefore not reaching EC50, also suggesting a possible nutrient function of the treated water. Consequently, the treated water by elC could, for example, has potential for non-potable use. ConclusionsThe study made it possible to prove the efficiency of elC treatment (72%, 99.79%, 85%, and 87.36% for SO42−, Fe, Mn, and Al, respectively), the importance of post-treatment toxicological assessments, and the potential of the duckweeds as an option for a test organism in these types of evaluations. Statement of noveltyThis paper with duckweed enabled the identification of the most suitable treatment to allow the treated water to be (re)used, since both treatments presented high efficiencies in terms of sulfate, acidity, and metal removals. This approach therefore gives a complementary view of the treatment then beyond complying with current environmental legislation to the treated effluent.

Removal of Molybdenum from Mining-Impacted Water by Sorption onto Manganese-Rich Sludge

Removal of Molybdenum from Mining-Impacted Water by Sorption onto Manganese-Rich Sludge

EVALUATION OF SPIROGYRA SP. AS A BIOINDICATOR OF HEAVYMETAL POLLUTION IN A TROPICAL AQUATIC ENVIRONMENT

Due to the wide occurrence of environmental pollution, heavy metals need to be closely monitored in the aquatic environment because of its ecotoxicological effects on biota. In this regard, biomonitoring as a tool for the assessment of metal pollution in aquatic ecosystem is quite appealing. Therefore, this study was conducted to investigate algae as a potential bio indicator ofheavy metal pollution in an aquatic environment in Fiji. Spirogyra sp. was sampled from a mining impacted water resource and analysed for heavy metals (manganese, copper, chromium, lead and zinc) using atomic absorption spectrometry. The order of metal accumulation in Spirogyra sp. wasfound as Mn &gt; Cu &gt; Cr &gt; Pb &gt; Zn. The results show that Spirogyra sp. is capable of accumulating heavy metals from polluted water and may be used a bioindicator species in environmentalmonitoring. Finally, the elevated heavy metal levels in the VGR aquatic environment could posean ecological risk and appropriate remediation strategies are recommended to minimise adverse impacts to aquatic life.

Role of the substrate on Ni inhibition in biological sulfate reduction

In treating mine-impacted waters using sulfate-reducing bacteria (SRB), metal inhibition and substrate selection are important factors affecting the efficiency of the bioprocess. This work investigated the role of the substrate (i.e. lactate, formate, glycerol and glucose) on Ni inhibition to SRB with sulfate-reducing activity tests at initial pH 5, 7 and 9 and 100 mg/L of Ni. Results indicated that the type of substrate was a significant factor affecting Ni inhibition in SRB, which was the most negligible in the lactate system, followed by glycerol, glucose, and formate. Although less significant, Ni inhibition also varied with the pH, leading for instance, to a reduction of 77% in the sulfate reducing activity for the formate system, but only of 28% for lactate at pH 5. The added substrate also influenced the precipitation kinetics and the characteristics of the precipitates, reaching Ni precipitation extents above 95%, except for glucose (83.2%).

Geochemical and hydrological evolution of mine impacted waters at the Argyle Diamond Mine, Western Australia

The lamproite ore body at the recently closed Argyle diamond mine is geochemically benign, but the surrounding sedimentary sequence contains two thin pyritic black shale beds that are prone to acidification. Although the waste rock is on average net neutralizing, some localized acidification and sulfate release was first observed in 1999 after 15 years of open pit mining. Contact and receiving water quality have been actively managed and monitored for 20 years to further limit the already low environmental risks posed by nitrate, nickel, magnesium and sulfate. All four solutes exhibited increasing concentrations across the monitoring network during or shortly after the period of peak waste rock production from 1999 to 2004. Since open pit mining and associated rock blasting ended in 2013, concentrations of nitrate have declined by 50%–90% at most locations. Nickel concentrations have also declined by 30% at the two acidic waste rock seeps which account for 80% of the dissolved nickel load. Sulfate and magnesium concentrations generally peaked between 2010 and 2013 and have not exhibited any significant increasing or decreasing trends since then. Annual offsite sulfate release since 2014 has averaged about 0.4% of the total sulfur inventory stored on site. Future sulfate concentrations and loads are predicted to gradually decline as the remaining sulfur inventory is depleted. Even during the 2005 to 2008 period, when all solute release rates were near their maximum, the receiving aquatic ecosystems remained intact with only subtle changes to some invertebrate communities. It is clear that peak release rates have already passed. The geochemical evolution at Argyle is much more rapid than at most other large mines. This is likely due to several factors including: 1. the low mean sulfur concentrations in the black shales; 2. the short geochemical lag time in the reactive units; 3. the high annual rainfall; and 4. a black shale segregation program that was initiated in roughly 1996.

Evaluation of operating conditions on sulfate reduction from acidic wastewater in a fixed-bed bioreactor

The removal of sulfate derived from mine impacted waters is a major objective when treatment is focused on removing potentially toxic metals and metalloids, and neutralizing the acidity of these polluting waters. Here we report on the use of a mixed culture fixed-film column bioreactor including one acidophilic sulfidogen operated for 270 days to primarily remove sulfate from an acidic synthetic water that contained a low level of zinc (0.15 mM). Changing the hydraulic retention time (HRT) from 100 to 30 h caused minor perturbations in the removal of sulfate (∼40%) using 6 mM of glycerol as carbon and electron source; however, lowering the HRT to 25 h did not sustain biosulfidogenesis. By increasing the concentration of glycerol as electron donor to catalyze the dissimilatory reduction of sulfate, it was possible to reduce the concentration of sulfate from 14 mM to ∼3 mM. This corresponded to an ∼80% removal efficiency from the acidic water feedstock, which is well below the lowest attainable concentration using conventional technologies such as gypsum precipitation. Molecular analyses of the column effluent demonstrated that the mixed culture population changed with varying concentrations of glycerol, highlighting a role for Clostridium sp. in the degradation (removal) of acetate produced in the bioreactor by Desulfosporosinus acididurans.

Mine-impacted water: From waste to resource

For many years, mine-impacted water has been regarded as a problem and linked to long-term environmental liabilities. However, this water can be a renewable and a sustainable resource, provided that it is managed in a responsible and sensible manner. South Africa's National Water Resource Strategy (NWRS, 2013) considers water that can be used to contribute to economic activity to be a water resource. Although all water resources are considered as belonging to the State, government does not appear to have meaningfully explored the use of mineimpacted water to contribute to the country's economic activity. Africa is blessed with more sunshine than anywhere else, apart from Australia, yet we see no rollout of vast quantities of solar panels to ensure every African family has access to affordable power. This suggests that governments are incapable of managing such a free resource. At the same time, apart from the equatorial areas, water is a seriously constrained resource and yet we expect the same entities to manage a commodity none of us can live without. This paper explores the conversion of mine-impacted water from waste to a resource and how the inclusion of other stakeholders (such as water users, landowners, and ordinary South Africans) could benefit the process.

Production of nesquehonite, a magnesia precursor, by carbonation of synthetic mine waste water

Nesquehonite (MgCO3.3H2O) is the preferred precursor to the high value product magnesia (MgO). Magnesia is used extensively in the mining industry for the hydrometallurgical recovery of metals and is usually obtained from processing naturally occurring minerals, brines or sea water. The mining industry produces large volumes of mine-impacted water in the form of brines and other wastes that could be used as a low-cost resource for producing the magnesia precursor. This work aimed to optimise the first phase of a potentially low-cost MgO production process, by carbonation of a synthetic solution simulating a Mg-rich liquid mine-waste. A three-factor, two-response, Box-Behnken response surface methodology experimental design (RSM) was used to determine the optima for the process on a synthetic sample. The optimal factor settings were identified and the tests established that the target product, nesquehonite, was preferentially formed in the majority of the experiments.